Electro-mechanical decoder



Filed Aug. 8, 1955 c. o. BARNHART 2,794,969

ELECTRO-MECHANICAL DECODER June 4, 1957 2 Sheets-Sheet 1 June 4, 1957 c. o. BARNHART 2,794,969

ELEcTRo-MECHANICAL. DECODER Filed Aug. 8, 1955 2 sheets-sheet 2 f u INI/ENTOR. v- E "L E] 2 C af/vf a. 5,9 Mmm y BY WML;

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United States Patent ELECTRO-MECHANICAL -DECODER AClarence OJ'BarnharL/RomefN. Y., -assignor to the-United AStates of -America as represented fby the Secretary of Vthe Air Force Application August '8, 1955, Serial No. 527,185

"2 Claims. v(Cl."540"164) (Granted vunder Title 35, U. S. Code (1952), sec. 266) Theinvention describedherein may be manufactured and used by `or for the UnitedStates Government forgovernmental purposes without payment to me of :any royalty thereon.

The decoder described herein `operates in response to the occurrence of a predetermined serial electrical binary codein two circuits to perform a desired function such as closing `an electric circuit. The-code consists of a .sei-.ies of venergizations of the two circuits, cachenergization being of one or the other but not both circuits. "The duration of an energization land the interval between successive energizations are immaterial.

Briey, the decoder comprises a shaft, ratchet means for rotating the shaft a step :at a time and a code wheel carried by the shaft. Cooperating with the code wheel and actuated thereby is a switch which is capable of connecting each of the two circuits to either the ratchet means for :advancing the shaft `or a resetting means for returning the shaft to its zero `or start position. The switch is further designed so that 'if `one of the circuits is connected to the ratchet means the other is connected to the resetting means, and vice versa. If the two circuits are energized in the sequence prescribed by the code wheel the shaft continues to advance until the last fstep, corresponding to the last element of the code, causes `a switch to be actuated which closes 4an output circuit and also actuates the resetting means, returning the decoder to its start position. If, on the other hand, the energization does not follow the prescribed sequence, :at the rst departure therefrom the resetting means is actua-ted returning the decoder to its start position.

A more detailed description of the invention will be given in connection with a specific embodiment thereof shown in the raccompanying drawings in which:

Fig. 1 is a `schematic diagram of the decoder, and

Figs. Za-b-c show details of the clutch used in the decoder.

Referring to Fig. 1, the decoder has a shaft 1 which carries a code wheel 2, a cam 3 and a clutch disc 4. The code wheel is shown in its rstart position toward which it is biased `at all times yby `reset spring 5, the pin 6 resting against ystop 7 in this position. A lsecond shaft 8, piloted in the end of shaft 1, carries ratchet wheel 9, a collar 10 for actuating switch 11, a thrust collar 12 and a stop collar 13. Shaft 8 enters reset solenoid 14 through guide 15. Ratchet wheel 9 is constantly urged toward clutch disc 4 by spring 16 acting through thrust bearing 17 and thrust collar 12. Solenoid 14 operates when energized to move shaft 8 to the right against the laction of spring 16 until collar 13 strikes guide 15.

The clutching arrangement existing between disc 4 4and ratchet wheel 9 is `shown in Figs. Za-b-c. Wheel 9 has a plurality of openings 18 at the same radius as pin 19 in disc 4. These openings are equal in number to Iand in angular alignment with the ratchet faces. When solel noid 14 is deenergized, as 'shown in Fig. 1, ratchet whee19 is held against disc 4 by spring 16 and shafts 1 and 8 2,794,969 Patented June 4, 1957 rice are locked together by pin 19 which enga-ges one of the openings 'in 'the ratchet wheel. When lsolenoid 14 is energized, ratchet wheel V'9 is moved sufficiently far to theright to disengage pin 19 as shown in-Fig. '2c'. Whenever .the clutch is disengaged, shaft 1 an-d code wheel 2 return to the start position under the influence of spring 5.

The code Wheel `2 is in the fform of :a two-level cam which actuates switch 20. The two input circuits to the decoder are connected to terminals A and B `of this switch, 'C being the common terminal. When switch 20 -is in its upper position terminal A is connected to step solenoid 21 and terminal B is connectedto reset solenoid 14. In the lowerposition of switch 20 the conditions are reversed so that terminal A is connected to the reset solenoid and terminal B to the step solenoid. The two cam levels are distributed about the circumference of the wheel 2 in accordance with the prescribed code which, in the speciiic example shown, is ABBABAAB, the letters referring to the terminal that is energized. The angular extent of the cam surface devoted to each code element is indicated on the code wheel in`Fig. l and is equal to the angular spacing `between the 4ratchet faces of ratchet wheel 9.

AIf vthe code 'wheel `2 is rotated counterclockwise beyond the last code element '(B), pin 6 actuates switch 22 which applies voltage from source 23 to output terminal O and `also to reset solenoid 14.

A step-by-step counterclockwise rotation of shaft 1 and code wheel 2 is achieved through step solenoid 21 which actuates pawl 24. Pawl 25 prevents reverse rotati-on of shaft 1 under the influence of spring 5 when the clutch 4-9 is engaged. The alignment of the various parts is such that in the rest position of ratchet Wheel 9 the follower 26 of switch 20 rests -in the center of a code element cam surface, as shown in Fig. l. One energization of step solenoid 21 causes code wheel 2 to advance Iin a counterclockwise `direction by an amount equal to the distance between the centers of adjacent code element cam surfaces.

As already indicated, energizations yof reset solenoid 14 disengages clutch `4 9 and allows code wheel 2 to be returned to its start position by spring 5. In order to insure that solenoid 14 remains energized and clutch 49 disengaged until code wheel 2 has had time to return to its start position =a reset interlock circuit comprising switches 11 and 27 is provided. Switch 11 is actuated by collar 10 on shaft 8 and is closed whenever clutch 4-9 'is disengaged. Switch 27 is actuated by cam 3 and is closed lat all times except when Wheel 2 is in the start position. Therefore, Iif clutch 4-9 is disengaged by solenoid 14 while code wheel 2 'is in other than its start position a circuit is completed from source 23 through Iswitches 27 and 11 which supplies current to the solenoid until Wheel 2 has returned to its start position and switch 27 ha-s Iopened.

Considering the operation of the decoder, if terminals A and B are energized in the sequence prescribed by the code wheel, which in the case illustrated in ABBABAAB, the code wheel is advanced one step in the counterclockwise direction (Fig. l) for each energization. For example, with code wheel 2 in its start position terminal A is connected to step solenoid 21 so that energization of this terminal causes code wheel 2 to advance to its second position. In the second position terminal B is connected to solenoid 21 and energization of this terminal causes wheel `2 to advance to its third position. The code wheel continues to advance in this manner if the terminals continue to be energized in accordance with the code prescribed by the code wheel. When the code Wheel has finally reached `the `last code element position, in the illustrated case a B position, the iinal energization of the B terminal advances the code wheel Ione more step causing pin 6 (Fig. l) to actuate switch 22 and apply voltage to l return to its start position.

If terminals A and B are not'energized in the sequence prescribed by the code wheel, the decoder is reset to its start positionat the irst `departure from the prescribed sequence. This will be clear fromrFig. 1 where it isapparent that if for any position of the code wheel `other than its start position the terminal opposite to that speciiied by the code wheel in that position is energized, this energization will be applied to reset solenoid 14 rather than to step lsolenoid 21 and will result in return of code wheel 2 to its start position.l

I claim: v

1. In combination with a pair of electric circuits that may be energized one cir-cuit iat a time in any sequential order, yapparatus for determining if said circuits are enerf ygized n times in a predetermined order, said apparatus comprising: a code wheel having said predetermined order ystored along its circumference in the form of a two-level cam extending over n adjacent equal sectors of said wheel, the cam in any `sector having one of two levels, the upper level corresponding to one of said circuits and the lower level corresponding to the other of said circuits; means defining a start position for said code wheel; spring means constantly biasing said code wheel toward said start position; a ratchet wheel having ratchet faces with an angular `separation equal to the angle of said sectors; normally engaged clutch means between said ratchet Wheel `and said code wheel; electrical-ly `operated pawl means for rotating said ratchet wheel and said code wheel through said normally engaged clutch in the direction yopposed to said spring means; electrically operated means for disengaging said clutch; and switching means actuated Iby said cam and `operating in the upper level `of said cam to connect said one circuit to said pawl means :and said other circuit to said clutch disengaging means iand operating in the lower level yof said cam to interchange said connections.

2. Apparatus as claimed in claim 1, in which there are provided a switch Iassociated with said code wheel and closed except in the start position of said `code wheel and a switch associated with said clutch and closed when said clutch is disengaged, and in which means are provided for energizing said clutch disengaging means through said switches in series.

References Cited in the tile of this patent UNITED STATES PATENTS 1,655,689 Chauveau Jan. 10, 1928 2,095,688 Ballentine Oct. 12, 1937 2,446,943 McGoin Aug. 10, 1948 

